With the advances of technology, touch display device has been widely used in various electronic devices. Basically, the touch display devices can be categorized into the following: resistive, capacitive, optical, acoustic wave and electromagnetic types. The optical touch display device is configured to have its touch panel disposed on a display panel and thereby, through disposing a plurality of infrared light sources, each of which is configured to emit infrared light beams, forming a light grid on the surface of the touch panel. In addition, the optical touch display device is further provided with a plurality of light sensors, corresponding to the infrared light sources, configured to sense the infrared light beams. According to this specific structure for the optical touch display device, a portion of the light grid may be blocked and accordingly the light or illumination intensity of the infrared light beams may result in light intensity variations while the surface of the touch panel is being touched by an object; and consequently, the optical touch display device can determine the touch point of the object on the touch panel according to the variations of the infrared light beams sensed by the light sensors.
Due to being capable of being controlled via a user's finger or a touch pen, the optical touch display device gradually is used in some compact electronic apparatuses. Therefore, developing an optical touch display device having a smaller size and a lighter weight is an important issue to those ordinarily skilled in the art.